Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".
With V7 as you have done you use magick instead of convert but you do not need the convert as well as that could be using a V6 version. If you allowed the install to add the Imagemagick path to the environmental variables you do not need the path. It may not make a difference but try:
You have shown PNGs rasterized from the SVG, but not the SVG itself. So we can't test it, or comment. Perhaps your meridian circles were drawn filled with white.
Are you using inkscape as the delegate? Adding "-verbose" to the command before reading the SVG will tell you.